The darkly beautiful, never-quite-famous, 63-year-old Francesca Annis arrives at the Young Vic swinging a bicycle helmet and tucks herself up beside me on the sofa. She is wearing a white linen shirt over jeans with her hair pinned up and reminds me of Isabel Allende. Not that they look alike, but Annis is half Brazilian and has the same intelligent, frank sensuality of those Latin women who go on being sexy into their sixties and seventies.

She has come from rehearsals for Under the Blue Sky, in which she plays one of a pair of teacher colleagues engaged in a long-term, slow-burn relationship. “They've been away together for six years running and not shared a bed.” Which may disappoint those who remember Annis as a naked Lady Macbeth in the Polanski film, as the sexually voracious Madame Bovary, as Anna romping with her much younger lover in Reckless and as a smouldering Gertrude, mother to Ralph Fiennes's Hamlet. The onstage oedipal attraction developed into a ten-year, real-life relationship, ending Fiennes's marriage and Annis's 23-year partnership with the father of her three children. (They split up in 2006 amid rumours of Fiennes's affair with a Romanian singer).

While his was the more bankable name, Annis continued to deliver a class act - recently as Lady Ludlow in Cranford. She never wanted to be a great big star, she says, adding: “Which is lucky because I'm not.” She scuppered a promising career in Hollywood by turning down offers including a Playboy centrefold to promote Macbeth. “I wasn't hungry enough to exploit my sexuality,” she says, “and I think you really had to do that. Also I am no fool - I could see I wasn't going to be offered the very best parts.”

Anyway, she had so many alien experiences. She tells me a chilling story about visiting a gynaecologist in LA because she felt rotten with her third pregnancy. “He asked me my age, symptoms, how many children I had - all that, and I answered dutifully. Eventually he said, 'Yes, OK, I think we can do it.' He was offering to get rid of the baby. He'd just thought: actress, in her forties, two kids already - she wants a termination.” Hollywood, she decided, was not where she wanted to be.

So she came to Kensington, close to the block of flats where she grew up and where her 96-year-old mother still lives. “My grandmother was on the sixth floor, my father's aunt on the second floor; there was my mother's best friend Olga and great aunt Lily - I never could get in the lift without meeting someone who'd known me all my life.”

Her own three children, now in their twenties, are back living at home. “Of course I don't want them to stay for ever,” she says. “But it's lovely - they are so grown-up and they look after each other. It doesn't matter what happens to me now - well, except I have to stick around to look after my mother.”

Earlier this year Annis starred in The Glass Menagerie in Dublin where, she confesses, she felt lonely. “People were very kind, inviting me to dinner, but it was companionship at home I was missing.” Are she and Fiennes not back together? She shakes her head: “I don't want to talk about him.” But there were rumours last year of a reconciliation ... She holds up both hands, palms outward: “No, no, no. He is somewhere in Romania probably.”

The hurt, if unstated, is palpable: would she be chary of sharing her life with someone again? “Oh no, come on,” she chides. “You have to have backbone.” She is happy being alone at the moment, she says, “but living closely and intimately with someone is the most fulfilling thing for homo sapiens”.

She is doing more theatre now, she says, because there are fewer TV and film parts for women of her age. “The script arrives and you want to love it but then it's dire and you can't do it.” Anyway, she says, “I like not working.” She is alarmed by the emphasis on twin goals of success and happiness: “It's an American import; really you just muddle through - like the Cavafy poem, Ithaca, you know: the journey of life is the thing, not the arriving.”

Under the Blue Sky is at the Duke of York's Theatre, London (0870 0606623). Previews from tonight

Editor's choice

• Live fast, die young: The 27 Club
• Madonna's 50 most memorable moments
• Proms Podcast with Pierre Boulez